Created
September 8, 2016 13:29
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Code dojo solution for Week 4 with @sofiajeanne
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import Control.Monad.Trans.State | |
import Data.Map.Strict as Map | |
import Data.Set as Set | |
triangle n = sum [1..n] | |
factors n = [f | f <- [1..n], n `mod` f == 0 ] | |
addFactors :: Int -> Int -> Map.Map Int (Set.Set Int) -> Map.Map Int (Set.Set Int) | |
addFactors n i factorMap | |
| n == i = Map.insert n (Set.fromList (factors n)) factorMap | |
| otherwise = case () of | |
_ | Map.member n factorMap -> factorMap | |
_ | n `rem` i /= 0 -> addFactors n (i+1) factorMap | |
_ | n `rem` i == 0 -> let | |
q = n `div` i | |
factorMap' = addFactors i 2 factorMap | |
factorMap'' = addFactors q 2 factorMap' | |
qFactors = factorMap'' Map.! q | |
qMultiples = Set.map (*i) qFactors | |
nFactors = Set.union qMultiples qFactors | |
in Map.insert n nFactors factorMap'' | |
factor1 = Map.singleton 1 $ Set.singleton 1 | |
factorCount n = do | |
knownFactors <- get | |
let updated = addFactors n 2 knownFactors | |
put updated | |
return $ Set.size $ updated Map.! n | |
main = print $ triangle . fst . head $ Prelude.filter ((>500) . snd) $ | |
zip [10000..20000] $ evalState (mapM (factorCount . triangle) [10000..20000]) factor1 |
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